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Abstract: The oxygen reduction reaction has been investigated on double-walled carbon nanotube (DWCNT) modified glassy carbon (GC) electrodes in acid and alkaline media using the rotating disk electrode (RDE) method. The surface morphology and composition of DWCNT samples was examined by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). Aqueous suspensions of DWCNTs were prepared using Nafion and non-ionic surfactant Triton X-100 as dispersing agents. The RDE results indicated that the DWCNT modified GC electrodes are active catalysts for oxygen reduction in alkaline solution. In acid media DWCNT/GC electrodes possess poor electrocatalytic properties for O2 reduction which indicates lack of metal catalyst impurities in the DWCNT material studied. The oxygen reduction behaviour of DWCNTs was similar to that of multi-walled carbon nanotubes (MWCNTs) observed in our previous studies. [Copyright &y& Elsevier]

Abstract: In this paper, the electrochemical reduction of oxygen has been studied on gold nanoparticle/multi-walled carbon nanotube (AuNP/MWCNT) modified glassy carbon (GC) electrodes in 0.5M H2SO4 using the rotating disk electrode (RDE) method. The AuNP/MWCNT catalysts were prepared by chemical deposition of AuNPs onto MWCNTs spontaneously grafted with 4-nitrophenyl groups. The composite electrode was characterised by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and cyclic voltammetry (CV). The oxygen reduction behaviour of these electrodes was compared with that of a bulk gold electrode. The AuNP/MWCNT catalyst showed a pronounced electrocatalytic activity towards O2 reduction in acid media. The half-wave potential of O2 reduction on the AuNP/MWCNT catalyst shifted ca 80mV to more positive potentials as compared to that of a polished Au electrode. The kinetic parameters of oxygen reduction were determined and the specific activity of the hybrid electrode was slightly higher than that of the bulk Au electrode. [Copyright &y& Elsevier]

Abstract: The electrochemical modification of the Ni electrode surface with nitrophenyl (NP) groups was performed by the diazonium reduction method. For the first time the barrier properties of NP-modified nickel surfaces were characterized using as a redox probe. Electrochemical measurements were carried out in 0.1M KOH containing 5mM K3Fe(CN)6 using cyclic voltammetry and the rotating disk electrode (RDE) technique. The nitrophenyl groups are strongly bonded to the nickel surface since they can withstand sonication in acetonitrile. The results of the X-ray photoelectron spectroscopy (XPS) analysis confirmed the irreversible attachment of nitrophenyl groups onto the nickel electrode surface. [Copyright &y& Elsevier]

Graphene layers grown by chemical vapour deposition (CVD) method and transferred from Cu-foils to the oxidized Si-substrates were investigated by spectroscopic ellipsometry (SE), Raman and X-Ray Photoelectron Spectroscopy (XPS) methods. The optical properties of transferred CVD graphene layers do not always correspond to the ones of the exfoliated graphene due to the contamination from the chemicals used in the transfer process. However, the real thickness and the mean properties of the transferred CVD graphene layers can be found using ellipsometry if a real thickness of the SiO 2 layer is taken into account. The pulsed laser deposition (PLD) and atomic layer deposition (ALD) methods were used to grow dielectric layers on the transferred graphene and the obtained structures were characterized using optical methods. The approach demonstrated in this work could be useful for the characterization of various materials grown on graphene. [ABSTRACT FROM AUTHOR]

A systematic study on the electrocatalytic properties of Pt nanoparticles supported on nitrobenzene-modified graphene (Pt-NB/G) as catalyst for oxygen reduction reaction (ORR) in alkaline solution was performed. Graphene nanosheets were spontaneously grafted with nitrophenyl groups using 4-nitrobenzenediazonium salt. The electrocatalytic activity towards the ORR and stability of the prepared catalysts in 0.1 M KOH solution have been studied and compared with that of the commercial Pt/C catalyst. The results obtained show that the NB-modified graphene nanosheets can be good Pt catalyst support with high stability and excellent electrocatalytic properties. The specific activity of Pt-NB/G for O 2 reduction was 0.184 mA cm −2 , which is very close to that obtained for commercial 20 wt% Pt/C catalyst (0.214 mA cm −2 ) at 0.9 V vs. RHE. The Pt-NB/G hybrid material promotes a four-electron reduction of oxygen and can be used as a promising cathode catalyst in alkaline fuel cells. [ABSTRACT FROM AUTHOR]

In this work, graphene and multi-walled carbon nanotubes were derivatised with anthraquinone (AQ) groups using spontaneous or electrochemical grafting of Fast Red AL salt. Glassy carbon (GC) electrodes were coated with AQ-modified carbon nanomaterials to study the oxygen reduction reaction (ORR). These nanomaterials were characterised by X-ray photoelectron spectroscopy and multilayer formation of AQ on the electrografted electrodes was observed. All the modified electrodes showed enhanced electrocatalytic activity towards the ORR in alkaline media. High AQ loading on the electrodes was found and the number of electrons transferred per O2 molecule was between 2 and 4. In addition, the stability testing of AQ-derivatised carbon nanomaterial-coated GC electrodes was performed. [ABSTRACT FROM AUTHOR]

The electrochemical reduction of oxygen on Pd nanoparticle-decorated nitrogen-doped graphene (Pd/NG) catalyst has been investigated in acid and alkaline solutions using the rotating disk electrode (RDE) method. The Pd/NG nanocomposites were prepared by NaBH4reduction. The surface characterisation of Pd/NG composites was performed by transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). The TEM images showed the uniform distribution of Pd nanoparticles over the N-doped graphene nanosheets. The RDE results indicated that Pd/NG catalysts possess a high electrocatalytic activity towards the oxygen reduction reaction (ORR). The prepared materials catalyse a 4-electron reduction of oxygen. The Tafel behaviour of O2reduction on Pd/NG catalysts was similar to that of bare Pd. The Pd/NG composite showed excellent ORR performance in alkaline media and is a promising material to be used as a cathode catalyst for alkaline membrane fuel cells. [ABSTRACT FROM AUTHOR]

Abstract: Fe phthalocyanine (FePc) and Co porphyrin (CoPh) modified reduced graphene oxide (rGO) nanosheets were used as non-noble metal electrocatalysts for oxygen reduction reaction (ORR). The surface morphology, graphitisation and surface composition of the catalyst materials were characterised by scanning electron microscopy, micro-Raman spectroscopy and X-ray photoelectron spectroscopy. Electrochemical experiments with FePc/rGO and CoPh/rGO catalysts were carried out in 0.1M KOH employing the rotating disc electrode (RDE) method. The RDE results show that both MN4-macrocycle/rGO modified glassy carbon electrodes are highly active for ORR in alkaline solution. [Copyright &y& Elsevier]

Abstract: Aryl layers on glassy carbon and gold electrodes were degraded by hydroxyl radicals from UV photolysis of hydrogen peroxide. The electrode surfaces were modified via electrochemical reduction of two structurally different azobenzene diazonium derivatives. The degradation of the aryl films was studied by AFM, XPS and electrochemical measurements using [Fe(CN)6]4− as solution probe. While the prepared aryl layers inhibited the electrochemical response of hexacyanoferrate, their degradation with OH radicals resulted in different electrochemical behaviours for glassy carbon and Au electrodes. The aryl layer on glassy carbon was thinned, indicated by the increasing reversibility of the [Fe(CN)6]4− response, whereas the aryl film on Au showed pinhole formation, indicated by the microelectrode behaviour of the hexacyanoferrate response without retarded reversibility. [Copyright &y& Elsevier]

Abstract: Three different azobenzene derivatives (azobenzene diazonium tetrafluoroborate, Fast Garnet GBC sulphate salt and Fast Black K salt) were covalently attached to glassy carbon (GC) electrodes by electrochemical grafting. The grafting of GC surfaces was controlled by varying the number of potential cycles during the modification procedures. The presence of azo groups on the modified electrode surfaces was confirmed by X-ray photoelectron spectroscopy. The electrochemical properties of the modified electrodes were characterised by cyclic voltammetry and the rotating disc electrode (RDE) technique using the redox system. The blocking behaviour of aryl films towards oxygen reduction was studied by linear sweep voltammetry and the RDE method. The blocking action of the aryl-modified electrodes for ferricyanide reduction was significantly greater than for O2 reduction. By estimating the parameter of relative blocking efficiency the best barrier properties were observed for azobenzene-modified GC electrodes. [Copyright &y& Elsevier]

The electrochemical properties of Au electrodes grafted with 4-nitrophenyl and 4-decylphenyl groups have been studied. The electrografting of gold electrode surface with aryl groups was carried out by electroreduction of the corresponding diazonium salts in acetonitrile. The nitrophenyl film growth on gold was examined by atomic force microscopy, electrochemical quartz crystal microbalance and X-ray photoelectron spectroscopy. These measurements showed that a multilayer film of nitrophenyl groups was formed. Cyclic voltammetry was used to study the blocking properties of aryl-modified gold electrodes towards the Fe(CN) redox system. The reduction of oxygen was strongly suppressed on these electrodes as evidenced by the rotating disc electrode results. [ABSTRACT FROM AUTHOR]

Abstract: The electrochemical response of 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) on aryl-modified glassy carbon (GC) electrodes has been investigated. The electrochemical modification of GC surface with 4-nitrophenyl (NP) and 4-carboxyphenyl (CP) groups was performed using the diazonium reduction method. The 4-aminophenyl-modified GC electrodes were obtained by electroreduction of NP films. The surface coverage of aryl groups was altered by varying the number of potential scans during electrografting experiments. The electrochemical behaviour of ABTS was studied on bare and aryl-modified GC electrodes using cyclic voltammetry and the rotating disk electrode (RDE) methods. Electrochemical measurements were performed in acetate and phosphate buffers (pH=4–8) to study the effect of pH on the electron transfer process. The response of ABTS was independent of pH for bare GC and GC/NP electrodes (modified by 20 electrografting scans), whereas a slight pH-dependence was observed for other electrodes. The strongest blocking action was observed for the NP-modified GC electrodes of higher surface coverage and the lowest for reduced NP films (modified by a single electrografting scan). [Copyright &y& Elsevier]

Abstract: The properties of electrochemically grafted gold electrodes surface have been investigated. Electrografting with 1- and 2-naphthyl, biphenyl and 4-bromophenyl groups yielded strongly attached layers and for the latter, electrochemical quartz crystal microbalance (EQCM) and atomic force microscopy (AFM) measurements showed that a multilayer film of bromophenyl groups was formed. This was confirmed by X-ray photoelectron spectroscopy (XPS). The blocking of electron transfer for several redox probes caused by the aryl-modification was investigated using cyclic voltammetry (CV). Oxygen reduction was studied using a rotating disk electrode (RDE) and the data also revealed a strong inhibition of this process by the attached aryl groups. The stability of these functionalised surfaces points to the strength of the Au–C bonds formed. [Copyright &y& Elsevier]

Platinum nanoparticles (NPs) were photo-deposited on SnO 2 -C nanocomposites prepared by sol-gel method. Surface morphology of the prepared materials, examined by scanning electron microscopy (SEM) and transmission electron microscopy, confirmed selective deposition of Pt NPs on SnO 2 nanoclusters formed on carbon surface. X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) analysis, cyclic voltammetry (CV) and CO stripping experiments revealed modification of the electronic properties of the Pt NPs photo-deposited on the oxide-carbon composite in comparison to Pt/C prepared by the carbonyl chemical route. Rietveld refinement was employed to identify existing phases of catalysts and to determine the crystallite size. Micro-strain and intrinsic stacking fault increased and decreased, respectively, as a function of crystallite size. Pt loadings were determined by inductively coupled plasma mass spectrometry (ICP-MS). The oxygen reduction reaction (ORR) activity of the electrocatalysts was investigated in acid media using the rotating disk electrode (RDE) system. Accelerated durability test (ADT) results showed that photo-deposited Pt nanoparticles onto SnO 2 -C nanocomposite are more durable than those chemically deposited on carbon. • Pt/SnO 2 -C composite electrocatalysts were prepared by photo-deposition. • For comparison, platinum nanoparticles were chemically deposited on carbon. • Metal-support interaction was studied by physical and electrochemical characterization. • Pt/SnO 2 -C catalysts showed high oxygen reduction activity in acid media. • Durability of the Pt/SnO 2 -C catalyst was superior in comparison with Pt/C. [ABSTRACT FROM AUTHOR]

Abstract: For the first time, the oxygen reduction reaction (ORR) is studied on pyrolysed electrospun multi-walled carbon nanotube (MWCNT) and styrene-acrylonitrile (SAN) composite fibre catalysts in alkaline medium. Scanning electron microscopy images revealed that the prepared catalysts mainly consist of MWCNTs, while nitrogen doping of the catalysts is confirmed by X-ray photoelectron spectroscopy. This indicates that SAN can be used as a nitrogen precursor. The ORR studies carried out by rotating disc electrode (RDE) and rotating ring-disc electrode (RRDE) methods showed that the prepared catalysts were considerably more active towards the ORR than the pristine MWCNTs.Graphical Abstract: [ABSTRACT FROM AUTHOR]

In this paper, aryl films are grafted via electrochemical reduction of two different diazonium salts, 4-nitrobenzenediazonium tetrafluoroborate and Fast Red AL salt, in different conditions on polycrystalline copper electrodes. For the surface modification, “normal” electrografting, redox grafting (RG) and for the first time, RG and rotating disk electrode combined method are used. The obtained aryl films are characterized by X-ray photoelectron spectroscopy and atomic force microscopy. Surface concentrations of redox active moieties are determined in acetonitrile and highest values of ca. 25 and 12 nmol cm −2 are obtained in case of nitrophenyl and anthraquinone films, respectively. Different aryl films exhibit unequal blocking action toward ferricyanide probe and also variable degree of inhibition of the O 2 reduction rate. [ABSTRACT FROM AUTHOR]

Acid-treated multi-walled carbon nanotubes (MWCNTs) were decorated with TiO 2 using the atomic layer deposition (ALD) technique followed by uniform distribution of platinum nanoparticles (PtNPs) through magnetron sputtering. Surface analyses were performed by scanning electron microscopy (SEM), scanning transmission electron microscopy (STEM) and X-ray photoelectron spectroscopy (XPS). Electrochemical decontamination and characterization of the Pt-TiO 2 /MWCNT electrodes were carried out by CO stripping followed by cyclic voltammetry in acid media. The oxygen reduction reaction (ORR) was studied in O 2 -saturated 0.05 M H 2 SO 4 solution using the rotating disk electrode (RDE) method. Durability of the prepared catalysts was examined by repetitive potential cycling. Electrochemical data obtained was analyzed and compared to that of the commercial Pt/C catalyst. It was revealed that the Pt-TiO 2 /MWCNT catalysts possess higher ORR activity and better durability as compared to that of the commercial Pt/C. [ABSTRACT FROM AUTHOR]

Nitrogen-doped graphene oxide supported silver nanoparticles (Ag/NGO) have been synthesised using three different methods. The prepared catalysts were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and electrochemically tested for oxygen reduction reaction (ORR) in alkaline solution. The Ag/NGO catalysts prepared by borohydride reduction showed the least degree of nanoparticle agglomeration and the material which was prepared using ascorbic acid yielded the biggest Ag particles. XPS revealed that the nitrogen to carbon atomic ratio was about 0.07 and EDS mapping showed that nitrogen was uniformly distributed over the graphene. The ORR on all the Ag/NGO catalysts proceeded via 4-electron pathway yielding water while on the support material, N-doped graphene oxide, the number of electrons transferred per O 2 molecule was lower than four. The mass activity of all Ag/NGO catalysts was determined to be at least twice higher than that of NGO. [ABSTRACT FROM AUTHOR]

The aim of this study is to compare the electrochemical behaviour of graphene-based materials of different origin, e.g., commercially available graphene nanosheets from two producers and reduced graphene oxide (rGO) towards the oxygen reduction reaction (ORR) using linear sweep voltammetry, rotating disc electrode and rotating ring-disc electrode methods. We also investigate the effect of catalyst ink preparation using two different solvents (2-propanol containing OH- ionomer or N,N-dimethylformamide) on the ORR. The graphene-based materials are characterised by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy. Clearly, the catalytic effect depends on the origin of graphene material and, interestingly, the electrocatalytic activity of the catalyst material for ORR is lower when using the OH- ionomer in electrode modification. The graphene electrodes fabricated with commercial graphene show better ORR performance than rGO in alkaline solution. [ABSTRACT FROM AUTHOR]

Manganese phthalocyanine (MnPc) and copper phthalocyanine (CuPc)-modified electrodes were prepared using multi-walled carbon nanotubes (MWCNTs) as a support material. The catalyst materials were heat treated at four different temperatures to investigate the effect of pyrolysis on the oxygen reduction reaction (ORR) activity of these electrocatalysts. The MWCNT to metal phthalocyanine ratio was varied. Scanning electron microscopy (SEM) was employed to visualise the surface morphology of the electrodes and the x-ray photoelectron spectroscopic (XPS) study was carried out to analyse the surface composition of the most active catalyst materials. The ORR was studied in 0.1 M KOH solution employing the rotating disk electrode (RDE) method. Glassy carbon (GC) electrodes were modified with carbon nanotube-supported metal phthalocyanine catalysts using Tokuyama AS-4 ionomer. The RDE results revealed that the highest electrocatalytic activity for ORR was achieved upon heat treatment at 800 °C. CuPc-derived catalyst demonstrated lower catalytic activity as compared to the MnPc-derived counterpart, which is in good agreement with previous literature, whereas the activity of MnPc-based catalyst was higher than that reported earlier. [ABSTRACT FROM AUTHOR]

In this work the electrocatalysis of oxygen reduction on iron and cobalt phthalocyanine modified reduced graphene oxide/multi-walled carbon nanotube (rGO/MWCNT) composite catalyst has been investigated. Modification of the carbon support was achieved by pyrolysing the mixture of rGO/MWCNT in the presence of metallophthalocyanine compounds at 800 °C. The surface morphology, graphitisation and surface composition of the catalyst materials were characterised by transmission electron microscopy (TEM), scanning electron microscopy (SEM), micro-Raman spectroscopy and X-ray photoelectron spectroscopy (XPS). The oxygen reduction reaction (ORR) was studied in 0.1 M KOH and 0.5 M H 2 SO 4 solutions on glassy carbon electrodes modified with MN 4 -macrocycle/rGO/MWCNT catalysts employing the rotating disk electrode (RDE) method. The RDE results show that both iron and cobalt phthalocyanine modified rGO/MWCNT electrocatalysts are highly active for ORR in alkaline solution while in acid media these materials exhibit only modest ORR activity. [ABSTRACT FROM AUTHOR]

Nitrogen-doped carbon aerogels containing transition metals have been used as non-precious metal catalysts for oxygen reduction reaction (ORR). The electrocatalysts were prepared by sol–gel polymerisation of organic precursors, followed by insertion of Co or Fe by ion exchange and subsequent carbonisation. The resulting materials were characterised by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). Electrochemical testing of the catalysts by thin-film rotating disk and ring-disk electrode technique revealed their high activity and stability in alkaline solution. Cobalt-containing aerogel showed slightly better performance than iron-containing material and the aerogel not containing transition metals was considerably less active. The Koutecky–Levich analysis indicated nearly four-electron reduction of O 2 on metal-containing nitrogen-doped carbon aerogels. The non-precious metal catalysts studied could be used as cathode materials for alkaline membrane fuel cells. [ABSTRACT FROM AUTHOR]

This work focuses on investigating the electrografting of chemical vapour deposition (CVD) graphene electrodes grown onto Ni foil (Ni/Gra) with different diazonium salts (including azobenzene diazonium tetrafluoroborate, Fast Garnet GBC sulphate salt, Fast Black K salt, 4-bromobenzene diazonium tetrafluoroborate and 4-nitrobenzenediazonium tetrafluoroborate). Various grafting conditions (e.g. “normal” electrografting in the narrow potential range and redox grafting in the wider potential range) were used. The electrochemical grafting behaviour was similar for all diazonium compounds used, except for the 4-nitrobenzenediazonium tetrafluoroborate when redox grafting was applied. The X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and Raman spectroscopy results confirmed the presence of the corresponding aryl layers on Ni/Gra surfaces. The formation of multilayers on Ni/Gra substrates was in evidence since the thickness of different aryl layers varied from few to 30 nm depending on the modification procedures as well as the diazonium compounds used and the XPS analysis revealed a peak at about 400 eV for all aryl-modified Ni/Gra samples suggesting the multilayer formation also through azo linkages. [ABSTRACT FROM AUTHOR]

Highlights: [•] O2 reduction was studied on GC electrodes modified with thick anthraquinone films. [•] AQ groups were electrografted onto GC surface using the diazonium reduction method. [•] The XPS analysis confirmed the presence of azo linkages within the AQ film. [•] The O2 reduction activity of the AQ films of various thickness was rather similar. [•] Two-electron reduction of oxygen to hydrogen peroxide was in evidence. [Copyright &y& Elsevier]

Highlights: [•] Single 5ns laser shots ablate CVD graphene with threshold fluence ~200mJ/cm2. [•] Damage threshold for UV irradiation depends strongly on sample. [•] Raman spectra indicate formation of oxidized graphene in ablated areas. [•] Oxidized graphene residues in ablated areas produce strong fluorescence. [ABSTRACT FROM AUTHOR]

Abstract: The oxygen reduction reaction has been investigated on acid-treated single-walled (SWCNT) and multi-walled carbon nanotubes (MWCNT) modified glassy carbon (GC) electrodes in acid media using the rotating disk electrode (RDE) method. Different acids were used for the carbon nanotube (CNT) purification. A systematic study was carried out to elucidate whether the metal catalyst impurities of CNTs play a role in the electroreduction of oxygen on the CNT modified GC electrodes. The surface morphology of the carbon nanotube samples was examined by transmission electron microscopy and the concentration of metal catalysts in the CNT materials was determined by energy dispersive X-ray spectroscopy. The acid-treated MWCNTs were also characterised by Raman and X-ray photoelectron spectroscopies. Aqueous suspensions of SWCNTs and MWCNTs used for GC surface modification were prepared in the presence of Nafion. The RDE results indicated that the acid-treated CNT modified GC electrodes are less active catalysts for oxygen reduction than as-received CNTs which could be explained by the absence of metal catalysts on the surface of purified CNTs. [Copyright &y& Elsevier]

Abstract: FIB-SEM, XPS and gas adsorption methods have been used for the characterisation of physical properties of microporous carbide derived carbon electrodes prepared from Mo2C at 600°C (noted as CDC-Mo2C). Cyclic voltammetry, constant current charge/discharge, and electrochemical impedance spectroscopy have been applied to establish the electrochemical characteristics for supercapacitors consisting of the 1M Na2SO4, KOH, tetraethyl ammonium iodide or 6M KOH aqueous electrolyte and CDC-Mo2C electrodes. The N2 sorption values obtained have been correlated with electrochemical characteristics for supercapacitors in various aqueous electrolytes. The maximum gravimetric energy, E max, and gravimetric power, P max, for supercapacitors (taking into consideration the active material weight) have been obtained at cell voltage 0.9V for 6M KOH aqueous supercapacitor (E max =5.7Whkg−1 and P max =43kWkg−1). For 1M TEAI based SC somewhat higher E max (6.2Whkg−1) and comparatively low P max (7.0kWkg−1) have been calculated. [Copyright &y& Elsevier]

Abstract: The electrochemical reduction of oxygen was studied on vacuum evaporated thin Pt films (0.25–20nm thick) on polycrystalline Au substrate (Pt/Au) in 0.1M HClO4 and 0.05M H2SO4 solutions using the rotating disk electrode (RDE) method. The surface morphology of Pt films was examined by scanning tunnelling microscopy (STM). The O2 reduction specific activity of Pt films increased with increasing the film thickness in HClO4, but was lower than that of bulk Pt even for the thickest films. In H2SO4, the specific activity showed no significant dependence on the platinum loading and was lower than in HClO4. The Tafel slope values characteristic to polycrystalline Pt (−120mVdec−1 and −60mVdec−1) were found for all electrodes. The RRDE studies of 0.5nm Pt/Au electrode revealed that O2 reduction predominantly proceeds through 4e− pathway and H2O2 is produced in low quantities. [Copyright &y& Elsevier]

Abstract: CuInS2 films were deposited by spray pyrolysis method at 350 °C. Films were characterized by XPS, AFM and electrical resistivity. The effect of chemical etchings in KCN and (NH4)2S2O8 solutions and thermal treatment at 530 °C in flowing hydrogen sulphide on the film surface composition has been studied. Indium oxide as main secondary phase in surface region of KCN-etched films is probably responsible of high surface conductivity and failure to prepare substrate configuration solar cell. Oxygen bounded to metal is present in the film bulk revealed by O1s BE of 530.0 eV of Ar+ sputtered profile. Hydrogen sulfide treatment transforms indium oxide into indium sulfide. Etching in ammonium persulfate solution has found to be effective to remove conductive upper layer resulting in surface with composition Cu:In:S=28.3:22.5:49.3. According to XPS, sprayed films show phase composition grading from the film surface to depth. [Copyright &y& Elsevier]